Add the lemongrass, galangal and kaffir lime leaves into the boiled water. Add Tom Yum Paste, stir and mix it with the water, then add tomatoes and shallots. Wait a few minutes for it to release all the herb flavors.

Toss in the shrimp, add Tom Yum Sauce, do a quick stir and then reduce the heat to low.

Add the mushrooms and let the soup boil for another minute.

Throw in a handful of chopped cilantro, and give the soup a final stir.